1. Field of the Invention
This invention relates to a light emitting device.
2. Background Art
Light emitting devices intended for lighting apparatuses including vehicle-mounted interior and exterior lamps and traffic signals are required to have higher brightness and higher light flux. In a light emitting device having a structure in which a light emitting element is bonded to the bottom surface of a recess provided in the lead, light emitted laterally from the light emitting element can be reflected upward by the beveled inner sidewall of the recess, which facilitates increasing its optical output.
Furthermore, the recess of the lead with the light emitting element bonded thereto is sealed with resin, such as silicone, to protect the inside. Silicone or other resin typically has a larger thermal expansion coefficient than the metal lead and the light emitting element.
When the light emitting device is mounted on a substrate, stress occurs at temperature rise and fall in the solder dip process and solder reflow process due to the difference in thermal expansion coefficient. For instance, in the cooling process, stress occurring due to contraction of the resin having large thermal expansion coefficient is applied to leads, chips, bonding wires and the like. This may cause peeling of the resin at the interface therewith, which may lead to degradation in optical and electrical characteristics and device failure.
JP-A-6-140550 (Kokai)(1994) discloses an example technique for avoiding cracks in a resin sealed package. In this example technique, cut-raised parts are formed in a tab. The resulting cut-out holes and cut-raised pieces are enclosed in a sealing resin, and their anchoring effect serves to avoid cracks.
However, application of this structure to a light emitting device makes it difficult to effectively extract light passing through the cut-out holes and interferes with increasing the brightness and light flux.